For travelling you can find prices at Qatar Airways holidays (www.qatarairways.com).
DVDs cost about QR90 per DVD. You can't really rent them here, the selection available is terrible.
A small car will cost you around QR1600 to rent (or you can buy one, of course).
For groceries you should budget about QR1500 per week to shop very well.
Eating out will cost you about QR400 for 2 people including a glass of wine.
Movies cost QR35 per ticket.